page_title: Ammeter
hierarchical_section_title: Ammeter
caption_attribution_description: Ammeter from New York Terminal Service Plant, 250 West Thirty-first Street, New York
context_page_description: An ammeter is a measuring instrument used to measure the current in a circuit. Electric currents are measured in amperes, hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters. Early ammeters were laboratory instruments which relied on the Earth's magnetic field for operation. By the late 19th century, improved instruments were designed which could be mounted in any position and allowed accurate measurements in electric power systems. It is generally represented by letter 'A' in a circuit.
context_section_description: An ammeter (from Ampere Meter) is a measuring instrument used to measure the current in a circuit. Electric currents are measured in amperes (A), hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters. Early ammeters were laboratory instruments which relied on the Earth's magnetic field for operation. By the late 19th century, improved instruments were designed which could be mounted in any position and allowed accurate measurements in electric power systems. It is generally represented by letter 'A' in a circuit.
caption: Ammeter from the old Penn Station Terminal Service Plant in New York City
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